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Reservoir Management


Largemouth KY Lake Roger Bitz

Fish Community Surveys

TWRA reservoir biologists spend many hours each year monitoring sport fisheries and forage fish communities. Because looking at the entire population of fishes in a lake is virtually impossible, biologists must depend on sampling to get a snapshot of population status and make predictions about how it will look in the future. Different sampling methods (electrofishing, nets, trawls) are used to sample fish populations. Targeted species surveys may be conducted to obtain information about fish population size structure, recruitment, growth, density, and mortality.

Information gathered from sampling surveys is coupled with information about the human and habitat components of sportfisheries and used to make management recommendations for harvest restrictions and/or stocking. Hatchery managers also use these gears to collect brood stock from wild populations which can be used in hatcheries to produce fish for stocking. The following section briefly describes sampling gear used by TWRA reservoir fisheries and hatchery staff.

Boat mounted electrofishers are used in Tennessee reservoirs to fulfill various sampling objectives.

Bass, crappie, and sunfish are highly vulnerable to this gear and surveys are normally conducted during the spring months.

A sampling design is chosen which reflects habitat diversity within a lake and fish are collected after being stunned by the shocking boat's electrical field.

Dip netters at the front of the boat pick up the fish and hold them in livewells for later analyses.

Gill nets are used for a variety of fish species that are difficult to sample with electrofishing gear.

TWRA uses them to collect sauger, walleye, white bass, striped bass, and Cherokee bass.

Most netting surveys are conducted during the winter months and may be targeted at pre-spawn runs.

Like other sampling methods gill net samples yield important insight into natural spawning success, success of stocking programs, and sizes of fish available to anglers.

Like electrofishing, seining is an active sampling method that allows biologists to look at forage availability, and survival of young sport fish.

Seines are really long, fine-meshed nets that are dragged through the water in shoreline areas.

Seine hauls have also been used by TWRA to evaluate stocking success of striped bass.

In recent years, TWRA biologists have been evaluating a surface trawl for sampling larval crappie.

This allows biologists to evaluate crappie spawning success in reservoirs where other gear types (namely trap nets) have not been an effective way to sample.

The specialized crappie net (neuston net) is dragged behind a boat for a fixed amount of time.

Larval crappie are later identified and counted back at the lab.

Often the work does not stop in the field for TWRA reservoir crews.

Fish samples often must be processed in the lab, species identified, and counted.

In addition, otoliths (ear bones) are routinely used by TWRA biologists to determine age structure and growth rates for sport fish populations.

Data must be entered into computer databases, analyzed, and summarized for reports.

The scenes below illustrate some of these activities.

Larval Fish From Neuston Net Sample
Larval Fish From Neuston Net Sample
Reading Otoliths Under a Microscope
Reading Otoliths Under a Microscope

Habitat Monitoring and Enhancements

In addition to monitoring fish population through annual surveys, TWRA biologists also monitor fish habitat changes and work to maintain healthy habitat conditions.   Water level changes are monitored throughout the year and water quality is monitored throughout the summer when high temperatures and low dissolved oxygen can pose a threat to sport fish and food fish.

Fish kills are documented by TWRA's Environmental Services Divisions after on-site surveys conducted by regional habitat biologists. In addition, TWRA staff meet with reservoir and tailwater regulators (i.e. Tennessee Valley Authority and U.S. Army Corps of Engineers) several times annually to discuss opportunities for data sharing and enhanced habitat protection.

TWRA's habitat enhancement projects for reservoirs fall into several categories: shoreline stabilization, aquatic macrophyte establishment, and fish attractor construction. Each of these categories has different objectives, but all are aimed at maintaining current conditions or improving conditions for fish and fishing. Over the years, TWRA has partnered with the public, TVA, and the Corps to work towards this end.

Tree plantings are one way that TWRA has worked to keep reservoir habitat in equilibrium. Planting trees in shoreline fluctuation zones helps stabilize banks and keep them from sloughing off into the water from wave action and flows. Reservoir biologists have long planted such water tolerant plants as bald cypress and button bush to keep shorelines intact and minimize erosion. This is especially useful in reservoirs with a lot of overbank habitat and little rock in the fluctuation zone. Trees are obtained from private nurseries and may be grown out at TWRA workbases so that they can withstand the elements and herbivores (e.g. beavers and deer) better when planted. Cypress trees in particular have extensive root systems which hold the shoreline together and the roots themselves may serve as nursery habitat for young fishes.

TWRA biologists construct different types of fish attractors that can be placed in reservoirs.   These devices do not normally enhance sport fish populations, but do provide structure around which fish can aggragate.  Bass, crappie, and sunfish utilize these attractors and anglers may key on these sites to increase their fishing success. 

The most common type of fish attractors used are sunken trees which can be weighted down to the bottom of a lake.   TWRA's Christmas tree habitat project in east Tennessee is a great example of how the Agency partners with anglers to build fish attractors.   Stake beds for crappie are also used in lakes with dense crappie populations and the right combination of bottom slope and composition.   Like, tree attractors, stake beds are marked by TWRA so that anglers know where they are located.

Spawning benches are a relatively new type of fish attractor for smallmouth bass. Unlike tree attractors or stakebeds, spawning benches have the potential to enhance smallmouth populations by providing more spawning habitat. They have been used in several deep reservoirs (e.g. Dale Hollow, Center Hill, Norris) to provide covered areas under which smallmouth build their nests. Research has shown that spawning benches built on rocky points are the most utilized by smallmouth bass.

Angler  Surveys

Fisheries management in Tennessee is based on information collected with sound methodology using the most contemporary techniques available within the community of fisheries professionals. Although the methods we use for obtaining information are sound and proven, there is no way to circumvent the inherent variability common to biological data. It is however, possible to validate our findings by comparing the results of multiple techniques. Commonly, we use angler surveys to compliment fish community surveys.

Angler surveys rely on fishermen to provide information about a fishery including, effort, catch, preferences, demographics, and economics. The information we collect through angler surveys gives us an unbiased sample of the angling population that we use in addition to our fishery independent assessments to select the best management plans to accommodate the widest variety of anglers.

Just as no single sampling method can be used to describe every fish population, (see fish community surveys), no single angler survey method can adequately represent all anglers or all components of a fishing experience. We therefore use several angler survey techniques to gain a comprehensive picture of the sportfishing population in Tennessee. The methods are described below:

The TWRA contracts annually with the University of Tennessee (UT) do an annual random survey of licensed anglers. A list of licensed anglers is provided to the Human Dimensions Research Lab at UT. From that list, a large random sample of anglers is contacted by telephone. The anglers are asked questions such as where they live, where the like to fish, the type of fishing they do, which species they like to fish for and their satisfaction with with fishing in Tennessee. The anglers are also invited to provide comments and suggestions concerning management of Tennessee Fisheries.

The Advantages to This Type of Survey Are:

  1. Provides unbiased randomly collected information about the entire angling population in Tennessee.
  2. Low cost per interview
  3. Good response rates

The Disadvantages Include:

  1. Recall Bias - this means that an angler may be asked questions about a fishing experience which occurred weeks maybe even months before the interview. The angler may not be able to accurately answer all of the questions due to the passage of time.
  2. A particular portion of the angling population may choose to not respond

Each year representatives from the TWRA approach anglers while they are fishing in order to ask them about their fishing experience that day. This process is known as a creel survey. The "creel clerks" ask anglers questions about the amount of time they have been fishing, what they are fishing for, what the have caught or released, where they are from, and questions about how much money was spent on the fishing trip. The information obtained is very useful to TWRA fishery biologists to make informed decisions regarding management of the states resources.

Currently the TWRA employs 11 full time creel clerks who conduct creel surveys on 17 reservoirs throughout Tennessee. Annually they collect between 10,000 and 15,000 interviews. In addition to reservoirs, various seasonal stream and tailrace surveys are conducted on an as-needed bases. The TWRA also contracts with the Tennessee Technological Institute from time to time to conduct specialized surveys where new research is the main focus.

The creel clerks may approach anglers by boat while they are in the process of fishing. This type of survey is known as a "roving creel survey". At other times the creel clerk may wait at a boat ramp, or pier to interview anglers at the completion of a fishing trip. This is known as an "access point creel survey". If you are approached by a creel clerk, pleasetake a few minutes to respond to an interview. This process allows you to have a voice in the management of Tennessees' fishery resources.

Advantages of Creel Surveys:

  1. No recall bias - anglers are not required to remember effort and catch from past fishing events
  2. High response rates
  3. Creel clerks are able to directly observe caught species. This allow for accurate identification and measuring of harvested fishes.

Disadvantages of On-Site Creel Surveys:

  1. It can be difficult to relate the information to the entire fishing population. For example, a reservoir creel survey would not represent stream or pond anglers.
  2. High cost per interview

The Tennessee Wildlife Resources Agencys' BITE (Bass Information from Tournament Entries) program is a coordinated effort between the Agency and organized bass clubs which hold tournaments in Tennessee.

Tournament organizers voluntarily submit their tournament data to the TWRA Fisheries Management Division via an online reporting form or a mail-in tournament report card. The information on the report form or card supplies information such as the location of the tournament, number of participants, total catch, and size and weight structure of the tournament catch. Annually, the information collected from tournament organizers is compiled into a report which benefits both the TWRA as well as tournament anglers.

The Advantages include:

  1. Information about bass stocks is compiled for major reservoirs
  2. Information about otherwise unknown tournament effort is provided to biologists
  3. Tournament anglers benefit by receiving information about bass tournament catch around Tennessee.

Disadvantages include:

  1. Information is provided only for a very specific portion of the fishing population.
  2. Catch, effort, and size structure may be proportionally greater than in the general fishing population